1. Field of the Invention
The present invention relates to a cellulose acylate film useful as an optical film or the like, and to its applications, more specifically, antireflection film, polarizing plate and an image-displaying device comprising the cellulose acylate film.
2. Related Art
As liquid crystal displaying devices have become more popular, the demand of the market on their displaying qualities and their durability have been more and more increased; and further improvement in terms of response speed and viewing angle properties, such as improvement of contrast and color-balance in oblique directions, has been required. For responding such demands, there has been provided various liquid-crystal modes; and research and development of retardation films, which can optically compensate birefringence of liquid-crystal layers employing such liquid-crystal modes respectively, are needed.
Cellulose acylate films have been widely utilized as polarizer protective films for liquid-crystal displaying devices, as having transparency and toughness. For example, proposed are optical films of fatty acid acyl cellulose esters such as cellulose acetate propionate, cellulose acetate butyrate, etc. (see JPA No. 2000-352620, referred to as Patent document 1). However, these films may have limited optical properties such as Re and Rth, and they may not always function adequately as a retardation film.
Also proposed is an optical film formed of a composition comprising a cellulose ester of mixed aromatic carboxylic acid (see JPA No. 2006-328298, referred to as Patent document 2).